Generally, a roll-to-roll plasma coating system produces devices by coating layers of thin film onto a web of substrate materials as the substrate material is continuously transported through different vacuum plasma coating chambers. Comparing with those conventional batch-type and inline-type plasma coating systems, roll-to-roll plasma coating systems can provide the most suitable thin film coating for high volume and cost-effective production. The use of a web of substrate materials for depositing has many advantages over other types of plane substrates. They are lightweight, flexible, durable, unbreakable and easily shipped products. And it helps tremendously in economizing on material and reducing the cost of process. Now the roll-to-roll coating systems have been already used in a wide range of industrial applications, including: food packaging, capacitor, flexible circuit board, PV solar cell, 3C product, solar control film, and so on.
Global warming induced by the emissions of greenhouse gases is one of the most critical environmental issues facing the world in recent years. Climate change will seriously affect life, environment and natural ecosystems on planet earth. Consequently, there are many technologies proposed to mitigate the damage of global warming, such as renewable energy, energy saving, energy efficiency improvement. And it is optimistic that global warming impacts can be mitigated.
In buildings sector, energy consumption is dominated by lighting, air conditioning and heating. It is responsible for approximately 30% of global energy demand. Thereby, reducing energy demand in the buildings sector plays a key role in reducing energy consumption. In order to reduce energy demand in building by regulating its temperature and illumination, building glazing can be coated with spectrally selective coatings which are able to transmit visible radiation and reflect infrared radiation. There are several commercial products currently available, such as Low-E glass, heat mirror and solar control film. However high-level products are too expensive for most peoples to install. From an economic point of view, it will inevitably demand a new low-cost thin film coating technology for solar control applications.
Multi-layer solar control films generally consisting of dielectric/metal/dielectric have been shown to have good properties, and can be produced on a large scale using vacuum magnetron sputtering technology. Reactive sputtering is widely used to prepare dielectric (metal oxide) layers thin films. In process, high flows of the reactive gases such as oxygen and argon are required for formation of metal oxide films during reactive sputtering of metal. However, metal oxide compounds are formed on the target surface and chamber wall at high flows of the reactive gases. These effects known as target poisoning and disappearing anode, lead to a decrease in the deposition rate and affected the composition of the film. The use of plasma process control of reactive gases and dual magnetron ac sputtering have made it possible to sputter dielectric (metal oxide) thin films at high deposition rates. However, the cost of associated equipment increases significantly.
In roll-to-roll production, moreover, it could take several tens of hours for coating lengths of several 1000 m web substrate. During sputtering, progressing erosion of the target material results in increasing strength of magnetic field at the target surface. Consequently, the depositing rate and composition of the deposited thin films are influenced. And a high-cost monitoring system is required to improve the stability of process.